Epoxy resins have many desirable properties which make them attractive as coatings, adhesives, paper release agents, additives for printing inks and for other applications. Included among these desirable properties are low viscosity, excellent clarity, high gloss and high reactivity.
Epoxy-modified silicone resins based on linear siloxy groups have also been prepared having improved heat-resistance, anti-corrosion resistance and water-resistance over the epoxy resins.
Mikami, U.S. Pat. No. 4,283,513, discloses siloxane-modified epoxy resin compositions comprising siloxane-modified epoxy resins, alkoxy functional organopolysiloxanes, and curing agents which have improved resistance to degradation of electrical properties by boiling water and moisture.
Mikami, U.S. Pat. No. 4,287,326, describes siloxane-modified epoxy resin compositions consisting essentially of siloxane modified epoxy resins, organofunctional alkoxysilicone compounds and curing agents which have improved degradation resistance to both electrical and adhesion properties when exposed to moisture or boiling water.
Liles et al., U.S. Pat. No. 4,082,719, disclose silicone epoxy curable compositions which teach the admixing of a small amount of an organosilicone compound containing at least one silicon-bonded hydrogen atom with curable compositions comprising a hydroxy-containing organosilicone compound, an epoxy compound and an aluminum compound to improve the curing performance of the compositions.
Crivello et al., U.S. Pat. No. 5,037,861, disclose cyclic epoxy functional siloxanes of the formula ((R'R")SiO).sub.n which has low initial viscosity yet are highly reactive in cationic photo-initiated polymerization reactions.
Hoffman et al., U.S. Pat. No. 4,707,529, disclose a dispersion of a siloxane polymer and optional dispersion stabilizer in an epoxy compound as a continuous phase, wherein the siloxane polymer is grafted to the epoxide compound. The patentees teach that the siloxane polymers which have functional groups capable of forming a graft with the epoxy compound continuous phase can include T-structure polydimethylsiloxanes having vinyl functionality(ies) at the branchpoint(s).
Special mention is made of Eckberg, U.S. Pat. No. 4,977,198, which teaches that UV curable epoxy functional organopolysiloxanes can be prepared by reacting organopolysiloxane hydrides with unsaturated epoxy groups in the presence of a platinum catalyst. Eckberg discloses that the epoxy functional silicones have an increased capacity to solubilized onium salt photoinitiators.
None of the references however teach or suggest the preparation of a branched epoxy-modified siloxane copolymerizate wherein the siloxane comprises a T or Q siloxy group. It has now been found that novel epoxy-modified branched silicones can be produced by reacting an epoxy with a T-structure or Q-structure silicon hydride compound, which have many excellent physical properties; and which are useful in forming improved copolymers with a variety of thermoplastic resins.